1. The Field of the Invention
The present invention relates to a seal system for use in a closed loop thermodynamic system. In more particular, the present invention relates to a seal system for capturing working fluid that has leaked or escaped from an expansion turbine and returning the escaped working fluid to a mixed working fluid thermodynamic cycle, such as a Kalina Cycle.
2. The Relevant Technology
Thermal energy can be usefully converted into mechanical and then electrical form. Methods of converting the thermal energy of low and high temperature heat sources into electric power represent an important area of energy generation. There is a need for increasing the efficiency of the conversion of such low temperature heat to electric power.
Thermal energy from a heat source can be transformed into mechanical and then electrical form using a working fluid that is expanded and regenerated in a closed system operating on a thermodynamic cycle. The working fluid can include components of different boiling temperatures, and the composition of the working fluid can be modified at different places within the system to improve the efficiency of energy conversion operation.
Typically multi-component working fluids include a low boiling point component and a higher boiling point component. By utilizing the combination of the low boiling point component and a higher boiling point component, an external heat source stream, such as industrial waste heat, can be more efficiently utilized for electricity production. Examples of a low boiling point component include water.
Once the working fluid has been heated, it is expanded at a turbine to convert the potential energy to mechanical energy which is utilized in the generation of electricity. One difficulty experienced at typical turbines is that working fluid can leak and escape to the ambient. This problem is exacerbated when one or more components of the working fluid are in a vapor or super heated vapor form. Leakage of working fluid can reduce the total volume of working fluid being utilized in a cycle. This can create additional complications where the working fluid is being utilized in a closed loop. Additionally, at times one component of a multi-component working fluid can leak in disproportionate amounts relative to the other components. As a result, the species balance of the multi-component working fluid can be interrupted. Where ammonia is utilized as one of the components of the working fluid, the release of ammonia to the atmosphere can be undesirable due to the material properties of ammonia. As a result, controlling release of either component can be highly desirable.
Turbine seal systems have been created to moderate fluid leakage problems. However, such seal systems typically require modification or wholesale changes to the turbine system to be effective. As a result, specialized turbines must be created based on the particular requirements of the heat source stream being utilized. This can render the turbines prohibitively expensive and/or interfere with desired operation of the turbine engineering. Additionally, some systems require vacuum or other pressures in the systems to be maintained at particular parameters. As a result of the overall system requirements can become more expensive than desired.